In many areas of research, medicine, physical training and rehabilitation, objective data describing an individual's ambulatory function is a useful indication of the individual's condition. Typically, information is obtained from an individual regarding their habits and abilities, and a subjective evaluation is conducted by a healthcare professional to assess the activity level of an individual. While such subjective evaluations are quick and inexpensive, the inherent subjectivity may lead to biased and inaccurate results.
Another approach comprises obtaining objective detailed measurements over short periods of time within a controlled laboratory setting. A detailed analysis of the aspects of an individual's gait, such as joint kinematics, ground reaction forces, electrical activity of muscles, or energy requirements of walking provide insightful quantitative information. Unfortunately, such measurements often fail to reflect the activity level of an individual going about normal daily life and the activities accompanied therewith.
Long-term measures of physical activity can provide meaningful quantitative indicators of an individual's condition and physical levels. A number of devices are commercially available to measure physical activity of an individual over an extended period of time. Such devices can provide a time-based breakdown of data and capture changing patterns of activity. A limitation to these devices is that they may only provide raw data or a degree of the activity level of an individual based only on the one or two variables. As a result, the devices to not take into account different behavioral patterns of the individual and may incorrectly grade an individual's activity level.